Fixes to the QoS object and docs relating to prefetch
Fixes to the QoS object and docs relating to prefetch

daevaorn/kombu,bmbouter/kombu,daevaorn/kombu,ZoranPavlovic/kombu,iris-edu-int/kombu,cce/kombu,mverrilli/kombu,tkanemoto/kombu,Elastica/kombu,bmbouter/kombu,Elastica/kombu,tkanemoto/kombu,numb3r3/kombu,numb3r3/kombu,celery/kombu,ZoranPavlovic/kombu,jindongh/kombu,cce/kombu,iris-edu-int/kombu,urbn/kombu,mverrilli/kombu,jindongh/kombu